On 07/23/2016 01:34 PM, Ameretat Reith wrote:
I'm trying to make three `Guy', `Father' and `Father1980' models mapped
to two `guys' and `fathers' tables. Fathers will inherit Guys and
Father1980 will inherit Fathers. So I coded it as:
|
fromsqlalchemy import(Table,Binary,ColumnasC,String,Integer,
ForeignKey,create_engine,MetaData)
fromsqlalchemy.orm import(mapper,relationship,backref,scoped_session,
sessionmaker)
metadata =MetaData()
db_engine =create_engine('sqlite:////tmp/test.db',convert_unicode=True)
db_session =scoped_session(sessionmaker(bind=db_engine))
classGuy(object):
pass
classFather(Guy):
def__init__(self,birth):
self.birth =birth
super(Father,self).__init__()
classFather1980(Father):
def__init__(self,*args,**kwargs):
super(Father1980,self).__init__(1980,*args,**kwargs)
guys =Table('guys',metadata,
C('id',Integer,primary_key=True),
C('type',String,nullable=False)
)
fathers =Table('fathers',metadata,
C('id',ForeignKey('guys.id'),primary_key=True),
C('birth',Integer)
)
father80s =Table('fathers_80s',metadata,
C('id',ForeignKey('fathers.id'),primary_key=True),
C('birth',Integer)
)
guysMapper =mapper(Guy,guys,polymorphic_on=guys.c.type)
fathersMapper =mapper(Father,fathers,inherits=guysMapper,
polymorphic_identity='plain-father')
mapper(Father1980,fathers,inherits=fathersMapper,
polymorphic_identity='young-father')
you have the wrong table above ("fathers" and not "fathers80s").
There's a bug here in how the ORM is corrupting the table in response to
this which I'll fix separately.
File"/venv/lib/python2.7/site-packages/sqlalchemy/sql/expression.py",line
2737,incorresponding_column
ifself.c.contains_column(column):
This is a very old version of SQLAlchemy, as starting with the 0.9
series the expression.py module was refactored to not be 4000 lines
long. If you're doing new ORM development and not just maintaining
legacy code, I encourage you to upgrade to version 1.0.
File"/venv/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py",line
612,in__get__
obj.__dict__[self.__name__]=result =self.fget(obj)
File"/venv/lib/python2.7/site-packages/sqlalchemy/sql/expression.py",line
2812,incolumns
returnself._columns.as_immutable()
AttributeError:'Table'objecthas noattribute '_columns'
|
If I map `Father1980' to table `fathers_80s' instead of table `fathers'
the error will go. I guess mapper didn't see `guys.type' from
`fathersMapper'. Can I make this working?
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